Rotor Unbalance Estimation with Reduced Number of Sensors

Abstract

Abstract:The most common cause of the excessive vibration in rotating machines is the rotor mass unbalance. If a machine vibration due to mass unbalance exceeds the alarm limits, then it may lead to machine failure. Therefore, rotating machines should be regularly checked to ensure that they are properly balanced. Currently, industries use the influence coefficient (IC) balancing technique for in situ machine balancing. The accepted practice is to use the vibration measurements in both vertical and horizontal directions at the machine-bearing pedestals together with the tachometer signal to estimate the machine rotor unbalance (both mass and phase angle). It is generally believed that the use of the machine vibration measurements in the vertical and horizontal directions represents better machine dynamics, and hence the estimated unbalance is likely to be more accurate. However, this paper applies the same concept of the IC method but with a reduced number of vibration sensors (one sensor per bearing pedestal at 45 • instead of two sensors at the vertical and horizontal directions). The use of one sensor per bearing pedestal at 45 • from both vertical and horizontal directions is likely to have responses from both directions. The reduction in the number of sensors by half will definitely save the instruments and their maintenance cost and reduce the computational effort in the signal processing significantly. The proposed concept is applied on a small-size laboratory rig with two balancing planes. The paper presents the unbalance estimations by using the measured vibration responses in both the vertical and horizontal directions simultaneously and using vibration responses measured at 45 • .

Vibration Analysis of a Roller Bearing Condition Used in a Tangential Threshing Drum of a Combine Harvester for the Smooth and Continuous Performance of Agricultural Crop Harvesting

“…Ji Jangtoa studied the interaction between the threshing unit and the plant materials, concluding that the amplitude of the vibration signal experienced the maximum elevation of amplitude on the horizontal radial axis (feeding direction)more than that of the vertical axis during the loading threshing condition [6]. The sensor mounted on the vertical radial axis encountered maximum vibration amplitude and the sensor mounted at 45 • with the horizontal radial axis is capable of displaying the vibration from the vertical and horizontal directions combined under no-load conditions [7].…”

Bulletin of the Polish Academy of Sciences: Technical Sciences

“…Some researchers such as Sinha et al [25,26], Edwards et al [27], and Lees et al [28,29] also proposed methods that can identify the unbalance parameters with a single measure- S. Bastakoti, T. Choudhury, R. Viitala, E. Kurvinen, and J. Sopanen ment, which makes them suitable for identifying the initial unbalance at commissioning stages as well. In more recent years, Shamsah et al [30] proposed a way for reducing the number of sensors for a given bearing location. Their study shows that a single sensor at 45 • angle can replace both horizontal and vertical displacement sensors for estimated unbalance.…”

The Application of the Bispectrum Analysis to Detect the Rotor Unbalance of the Induction Motor Supplied by the Mains and Frequency Converter

“…However, this is possible only when diagnostic signals, storing as much information about the machine condition as possible, are analyzed. The most frequently used diagnostic signals encompass: phase current [6][7][8][9], mechanical vibration [6,[8][9][10][11][12][13][14][15][16], axial stray flux [6], acoustic signal [16,17], and temperature [18]. The applications of high-calculation power systems enables diagnosing processes in real time.…”